1. Field of the Invention
The present invention relates to biometric filters and in particular to the use of filters in a system and method of generating a subset of enrolled biometric representations from a master database of enrolled biometric representations.
2. Description of the Related Art
The time and computational resources required to perform a biometric 1:N search of a master database comprising a plurality of enrolled biometric representations using a captured biometric representation can be prohibitively expensive. Increasing the number of independent biometric representations in the master database increases the length of time required to perform the search. A 1:N search is typically performed using a complex biometric matching algorithm by comparing a captured biometric data representation against each of the enrolled biometric representations in the master database. A numerical score is generated for each comparison and the enrolled biometric representations in the master database corresponding to the top-ranking scores are returned as the search results.
Filters are used to reduce the searching time by discarding those enrolled biometric representations which are unlikely to subsequently successfully match against the captured biometric representation. Biometric filters known heretofore are based on modality-specific features extracted from each enrolled biometric representation of the master database which can be quickly compared. For example, a known filtering technique with fingerprints is based on the high-level overall pattern formed by the flow of ridges in the fingerprint which are assigned to one of several classes, such as by using the Henry classification system. Other example finger-based filter techniques are based on the location of the core and delta points, the thickness of finger ridges, the number of ridges between specific locations, or the spatial relationships between specific points.
Filters known heretofore have reduced the length of time required to perform a search. However, since each filtering technique requires the extraction and comparison of modality-specific features, they are highly specific to certain environments, modalities, and biometric instances and cannot be used across multi-biometric databases.
Known arrangements relate to pre-assigning the biometrics to one of a number of available bins of like biometrics and then only searching the presented biometric against that specific bin. This requires an a priori classification of the biometrics and suffers in the same way as any statistical binning arrangement in that the usefulness of the final search will depend on the accuracy of the initial binning decision.